The percentage of peripheral blood eosinophils in normal individuals is <5% and the absolute value is <0.5×109/L. Due to the large physiological changes, it is best to take blood at 8 am. If the absolute value of eosinophils >0.5×109/L is called eosinophilia. According to the degree, it can be classified as mild (0.5~1.5×109/L), moderate (1.5~5×109/L) and severe (>5×109/L). Eosinophilia is a rare clinical disease with complex causes. We have summarized a set of diagnostic and differential diagnostic steps for clinical reference, combining years of experience and the latest literature, mainly from the following aspects.
I. Is it reactive?
Many factors can lead to increased eosinophil reactivity, including the following.
1. infections, mainly parasites, tuberculosis, chlamydia, HIV, etc.
2. drugs, such as anticonvulsants, antibiotics, sulfonamides, anti-rheumatic drugs.
3, allergic reactions, such as asthma, allergic rhinitis, urticaria, etc.
4, diseases of the whistling tract, such as allergic pneumonia, allergic bronchopulmonary aspergillosis and pulmonary eosinophilia
5, gastrointestinal disorders, such as eosinophilic gastroenteritis, allergic gastroenteritis, inflammatory bowel disease
6, connective tissue diseases, such as rheumatoid, scleroderma, and polyarteritis nodosa
7, neoplastic diseases, such as lymphoma, solid tumors, metastatic cancer, etc.
8, endocrine diseases, such as Addison’s disease, pituitary insufficiency.
9, immunodeficiency in graft-versus-host disease.
10, cytokine therapeutic response, such as IL-2, GM-CSF, etc. In conclusion, reactivity is mostly related to infection, allergy and autoimmunity, and this category of causes should be considered first in clinical practice, which can be confirmed by detailed history, physical examination, and relevant tests. If necessary, clonality should be excluded.
Second, is it clonal?
It refers to malignant hematological diseases or myeloproliferative neoplasms accompanied by eosinophilia, including those with.
1, acute myeloid or lymphoid leukemia.
2, chronic myeloproliferative disorders, such as chronic granulocytic leukemia, true erythrocytosis, primary thrombocytosis, primary myelofibrosis, chronic eosinophilic leukemia, chronic neutrophilic leukemia.
3. diseases with specific genetic abnormalities, myeloid or gonadal tumors with gene rearrangements (PDGFRα, PDGFRβ, FGFR1); systemic mastocytosis with KIT mutations.
4. myelodysplastic syndromes (MDS, MDS/MPN). Most of these syndromes have associated genetic, chromosomal, immunophenotypic, and cytomorphological changes, and most of them have clinical anemia, thrombocytopenia, and hepatosplenomegaly, etc. Relevant chromosomal, RT-PCR, FISH, flow cytometry, or bone marrow aspiration smear must be performed to determine the above etiology.
C. Is it idiopathic?
The cause is not known, but if there is eosinophilia with multi-system and multi-organ damage, eosinophils higher than 1.5×109/L for more than 6 months, which neither proves clonality nor excludes reactivity, it can be diagnosed as idiopathic eosinophilia and glucocorticoid therapy is effective.
Another familial eosinophilia, which is autosomal dominant, has rarely been reported clinically. If in doubt, family genetic investigation can be done.